Updated ASTRO Guideline Expands Pool of Suitable Candidates for Accelerated Partial-Breast Irradiation
On November 17, the American Society for Radiation Oncology (ASTRO) issued an updated clinical practice statement for accelerated partial-breast irradiation for early-stage breast cancer. The updated guideline reflects recent evidence that greater numbers of patients can benefit from accelerated treatment and also provides direction for the use of intraoperative radiation therapy for partial-breast irradiation. The update to the 2009 ASTRO consensus statement for accelerated partial-breast irradiation was published by Correa et al in Practical Radiation Oncology.
Early-stage breast cancer patients often receive radiation therapy following breast-conserving surgery to lower the chance of recurrence or metastasis, generally in the form of whole-breast irradiation using external-beam radiation delivered over several weeks. Accelerated partial-breast irradiation is a newer, localized alternative that delivers the effective radiation dose directly to the tissue at risk. This targeted therapy reduces treatment time and may limit adverse side effects, particularly those involving the heart and lungs. More than 75,000 women in the United States have received accelerated partial-breast irradiation since its introduction in the late 1990s.
Drawing on evidence published in the last 8 years, the guideline suggests that more breast cancer patients can benefit from accelerated partial-breast irradiation, including younger patients and those with low-risk ductal carcinoma in situ. The guideline recommends considering the following factors for the use of accelerated partial-breast irradiation outside of clinical trial settings:
- Age: Patients aged 50 or older should be considered suitable for accelerated partial-breast irradiation, patients aged 40–49 who meet other pathologic suitability criteria should be considered cautionary, and patients younger than 40 or those who do not meet the pathologic criteria should be considered unsuitable. The age cohorts in the original guideline were ≥ 60, 50 to 59, and < 50 years, respectively.
- Ductal carcinoma in situ status: Patients with low-risk ductal carcinoma in situ should be considered suitable for accelerated partial-breast irradiation if they meet all aspects of the definition of “low-risk” ductal carcinoma in situ from the RTOG 9804 trial, including screen-detected disease, low to intermediate nuclear grade, tumor size ≤ 2.5 cm, and surgical resection with margins negative at ≥ 3 mm. The original guideline did not allocate any ductal carcinoma patients to the suitable group.
- Surgical margins: There were no changes in surgical-margin criteria, maintaining the current standards that patients are suitable if surgical margins are negative by ≥ 2 mm, cautionary if margins are close or < 2 mm, and not suitable if margins are positive.
The update also provides guidance for the use of intraoperative radiotherapy for early-stage breast cancer patients, drawing on two large, phase III clinical trials that compared whole-breast irradiation with intraoperative radiotherapy. Partial-breast irradiation may be administered by a variety of methods, including brachytherapy, external-beam irradiation, and intraoperative radiotherapy. Recommendations for the use of intraoperative radiotherapy include:
- Physicians should counsel patients that the risk of ipsilateral breast tumor recurrence may be higher with intraoperative radiotherapy compared with whole-breast irradiation, based on evidence from both existing clinical trials.
- Electron-beam intraoperative radiotherapy should be restricted to patients with invasive cancer who are also considered suitable for partial-breast irradiation, based on data from a trial with 5.8-year median follow-up.
- Low-energy x-ray intraoperative radiotherapy should be used only in the context of a prospective registry or clinical trial and restricted to women with invasive cancer who are considered otherwise suitable for partial-breast irradiation. This recommendation reflects the short, 2.4-year median follow-up of existing trial data.
- Given the persistent risk of ipsilateral breast tumor recurrence over time, all patients treated with intraoperative radiotherapy should undergo routine long-term follow-up for at least 10 years to screen for tumor recurrence.
“As trials mature and evidence accumulates, we can understand more comprehensively who benefits from accelerated radiation treatment following lumpectomy, and we are finding that the pool of suitable candidates for this emerging treatment is larger than first anticipated,” said Jay R. Harris, MD, FASTRO, Chair of the task force that developed the guideline and Distinguished Professor of Radiation Oncology at the Dana-Farber Cancer Institute, Harvard Medical School. “Carefully selected patients may achieve similar tumor control following shorter, targeted schedules of radiation as they would with weeks of radiation to the whole breast.”
The guideline was based on a systematic literature review of studies published since May 2008, the last date searched for the original clinical practice statement. A total of 419 abstracts were retrieved from PubMed, and the 44 articles that met inclusion criteria were abstracted into evidence tables and evaluated by an 8-member task force of radiation oncologists, medical oncologists, and experts in intraoperative radiotherapy. The clinical practice statement was approved by ASTRO's Board of Directors following a 4-week period of public comment.
The content in this post has not been reviewed by the American Society of Clinical Oncology, Inc. (ASCO®) and does not necessarily reflect the ideas and opinions of ASCO®.
